This invention generally relates to a method and device for reducing combustor screech. More particularly, this invention relates to a flame holder that generates a radial phase variation that weakly couples to natural acoustic modes of the combustor.
Augmentors or “afterburners” provide an increase in thrust generated by a gas turbine engine. Fuel is sprayed into a core stream and ignited to produce the desired additional thrust. The fuel is fed into the core stream upstream of a flame holding device. The flame holding device provides a region of low turbulence to anchor and stabilize the flame within the high flow of the core stream. Combustor screech results when natural modes of the combustor couple with unsteady heat released by a combustion flame. Uniform heat release perturbation across the duct combines with the natural modes to produce the strongest screech. Noise attenuation features in the duct walls can dampen only portions of acoustic energy produces during combustion. Accordingly, it is desirable to develop methods and devices for reducing the generation and propagation of acoustic energy originating from the combustion process.